The short answer
Yes, mildly. NIAAA explains that alcohol suppresses vasopressin, a hormone that tells your kidneys to hold on to fluid, so you urinate more and lose extra fluid. The resulting mild dehydration likely adds to hangover thirst, tiredness and headache. The NHS suggests eating and having a glass of water before you drink, and a glass of water after every drink containing alcohol, to help prevent dehydration.
Key takeaways
- Alcohol suppresses vasopressin, the hormone that signals your kidneys to retain fluid, so you urinate more.
- The mild dehydration that follows likely contributes to thirst, tiredness and headache the next day.
- The NHS suggests a glass of water after every drink containing alcohol, and water and food before you start.
- Research has not found that extra electrolytes make a hangover less severe; the body restores its balance on its own.
How alcohol makes you lose fluid
NIAAA, the US government institute for alcohol research, explains the mechanism in its guide to hangovers. Your brain produces a hormone called vasopressin, which signals the kidneys to retain fluid. Alcohol suppresses its release. As a result, alcohol increases urination and the loss of fluid from your body.
NIAAA describes the result as mild dehydration, and says it likely contributes to hangover symptoms such as thirst, fatigue and headache. It lists dehydration as one of several things behind a hangover, alongside disrupted sleep, stomach irritation, inflammation and acetaldehyde, a toxic by-product of breaking alcohol down. So rehydrating can help with the thirst, but it does not undo everything else; our guide to hangxiety covers the rest of the hangover.
Signs you are dehydrated
MedlinePlus, the US National Library of Medicine's health site, defines dehydration as your body not having as much water and fluid as it needs, and lists the signs of mild to moderate dehydration:
- thirst;
- a dry or sticky mouth;
- not urinating much, and darker yellow urine;
- dry, cool skin;
- headache;
- muscle cramps.
When dehydration is an emergency
MedlinePlus says severe dehydration is a life-threatening emergency. Its signs include not urinating or very dark yellow urine, dizziness, confusion or irritability, a rapid heartbeat or rapid breathing, and listlessness. It says to call your local emergency number if a person loses consciousness or there is any change in their alertness, such as confusion.
That advice applies after drinking too. The NHS lists alcohol poisoning among the short-term risks of drinking too much, so if someone who has been drinking becomes confused or loses consciousness, call for emergency help.
How to stay hydrated when you drink
The NHS gives simple, practical advice across its alcohol pages:
- Eat something and drink a glass of water before you have alcohol.
- Have a glass of water after every drink containing alcohol, which it says will help prevent you becoming dehydrated.
- Alternate drinks containing alcohol with water or other non-alcoholic drinks.
- Do not drink on an empty stomach.
Do electrolyte drinks help?
Sports drinks and electrolyte products are popular after a night out. NIAAA says research has not found a link between how much a person's electrolytes are disrupted and how bad their hangover is, or evidence that added electrolytes make a hangover less severe. In most people, it says, the body quickly restores its electrolyte balance once the effects of alcohol wear off.
For dehydration in general, MedlinePlus suggests sipping water, or drinking water or sports drinks that contain electrolytes. Plain water is enough for most people after drinking; the bigger change is drinking less alcohol in the first place, which our guide on how to cut down on alcohol covers.
Common questions
Why does alcohol make you pee so much?
NIAAA explains that alcohol suppresses vasopressin, a hormone from the brain that tells your kidneys to hold on to fluid. With less of it, your kidneys let more water go, so you urinate more and lose extra fluid.
Does drinking water while drinking alcohol prevent a hangover?
It helps with dehydration, which the NHS says a glass of water after each drink will help prevent. It does not stop a hangover: NIAAA says the only way to fully avoid one is not to drink, or to keep alcohol to a minimum.
How do I rehydrate after drinking alcohol?
Sip water steadily, as MedlinePlus suggests for dehydration in general. NIAAA says the body usually restores its electrolyte balance quickly once alcohol wears off. Get emergency help if someone becomes confused or loses consciousness.
When to get help
This site offers self-help tools and information, not medical advice. Talk to a doctor, or call one of the lines below, if:
- you feel shaky, sweaty, sick or anxious when you haven't had a drink;
- you find it hard to stop once you start, or you want to cut down and can't;
- drinking is causing problems with your health, work or the people close to you.
Before you stop: It can be very dangerous to stop drinking suddenly if you are dependent on alcohol. If you get withdrawal symptoms, get medical help before you try to stop drinking.
Free, confidential helplines
- United States:SAMHSA National Helpline1-800-662-HELP (4357)Treatment referral and information, 24/7.
- United States:988 Suicide & Crisis LifelineCall or text 988Free and confidential support for people in distress, 24/7.
- United Kingdom:Drinkline0300 123 1110The national alcohol helpline, free and in complete confidence. Weekdays 9am to 8pm, weekends 11am to 4pm.
In an emergency, call your local emergency number.
Sources
- Hangovers. National Institute on Alcohol Abuse and Alcoholism (NIAAA). niaaa.nih.gov
- Dehydration (Medical Encyclopedia). MedlinePlus, US National Library of Medicine. medlineplus.gov
- Calories in alcohol. NHS. nhs.uk
- Tips on cutting down on alcohol. NHS. nhs.uk
- Alcohol-use disorder. NHS. nhs.uk
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